The additive antianginal action of oral isosorbide dinitrate in patients receiving propranolol. Magnitude and duration of effect.

Ten men with stable angina not completely relieved by full doses of propranolol (mean, 218 mg daily) were given double-blind, on alternate mornings, a placebo or an oral dose (5 to 30 mg) of isosorbide dinitrate (ISDN) previously titrated to lower sitting systolic blood pressure by 20 mm Hg. Patients had been trained in a protocol which precipitated angina after three to six minutes of bicycle exercise. On test days, with propranolol continued, bicycle exercise was performed until the appearance of angina before ISDN or placebo administration, and hourly thereafter for eight hours. Mean exercise duration was greater one hour after ISDN than after placebo by 182 sec (423 +/- 39 vs 241 +/- 13, p less than 0.001), and a difference of 63 sec was still present at six hours (p less than 0.002). At one hour, ISDN lowered resting systolic blood pressure by 26 mm Hg (from 114 +/- 5 mm Hg to 88 +/- 4 mm Hg; p less than .001) without appreciably changing heart rate. We conclude that ISDN is a very effective and reasonably long-acting antianginal supplement to propranolol.